1. Field of the Invention
The present invention relates to sanitary rotary valve for the powder or particle discharging system from receiving hoppers or other up-stream equipments to outside or down-stream equipments.
This device is used to discharge powder or particle quantitatively.
And, this device has another function to reduce gas flow through this device. Usually there is differential pressure between upper side and lower side of this device because powder is transported by gas flow.
The powder or particle relate to these devices are food or medicine taken by human or animals, or others that is required to be no contamination. And in case that different kinds of powder or particle is treated in same process line, this device is used to prevent mixing of kinds of powder or particle.
Inside of these devices is to be cleaned as regular maintenance to prevent contamination by rotted powder or particle of food or medicine, or to prevent mixing of different kind of powder or particle.
2. Description of the Related Art
With respect to a sanitary rotary valve for a powder discharging system, the valve as shown in FIG. 1 and FIG. 2 is used conventionally. FIG. 1 shows a sectional view of the sanitary rotary valve and FIG. 2 is a side sectional view of the sanitary rotary valve from a right side of FIG. 1,
wherein
    a casing 1, having horizontal hole, upper opening A and lower opening B, and    a side plate 2, having a center hole, and a box 2c on an outside surface, and    a door 3, provided on the opposite side of side plate 2, fixed to casing 1 by knobs 3a as detachable, and    a shaft 4, passing through the center hole of side plate 2, and    a rotor 5, having pockets C, and fixed to shaft 4 as detachable, and ball bearings 6a, 6b, between side plate 2 and shaft 4, and    a seal packing 7, between side plate 2 and shaft 4, and    a motor mount 8, fixed to box 2c of side plate 2 by bolts, and    a geared motor 9, fixed to motor mount 8 by bolts, and    a coupling 10, connecting shaft 4 and geared motor 9, and    a O-ring 11, between casing 1 and side plate 2, and    a O-ring 12, between casing 1 and door 3.
Usually flanges are provided on upper side and lower side of this device to be connected with other equipments or pipe lines.
The torque of geared motor 9 is translated to shaft 4 by coupling 10. One end of shaft 4 and one end of rotor 5 have hexagonal shape or key to fit each other, and translate rotating torque. Rotor 5 is fixed by a detachable screw nut 5a. 
To reduce gas flow through this device caused by differential pressure between upper side and lower side of this device, clearance between casing 1 and rotor 5 is required to be narrow such as 0.2 mm.
Casing 1 is sealed by seal packing 7, O-ring 11 and O-ring 12 to prevent leakage of inner gas and powder.
Powder or particle is dropped into pockets C through opening A by gravity, and turned by rotor 5, and discharged from pockets C through opening B by gravity.
Constant rotating speed of geared motor 9 makes discharging amount of power or particle constant.
When regular cleaning inside, door 3 is opened, and screw nut 5a is removed, and rotor 5 is extracted to outside. And inside of casing 1 and side plate 2, and rotor 5 is cleaned. After cleaning of them, rotor 5 is inserted into casing 1 and fixed to shaft 4, screw nut 5a is tightened, door 3 is closed, and operation is restarted.
However, there are two problems as for conventional sanitary rotary valve.
1) The Risk of Contamination
Shaft 4 is supported as a cantilever. Because, if journal to support shaft 4 is provided also on door 3, a lot of work is necessary to disassemble shaft 4 from journal of door 3 in each time of regular cleaning maintenance.
However, this cantilever supporting of shaft 4 causes deflection of shaft 4 by the reasons of wearing of ball bearings 6a, 6b, and/or force onto rotor 5 caused by irregular differential pressure between upper and lower sides of this device.
And in case of irregular raising up of temperature of powder or particle, the temperature of rotor 5 is raised up also, but the temperature of casing 1 is less than that of rotor 5 because casing 1 is cooled by outer atmosphere. The diameter of rotor 5 is increased by thermal expansion, but inside diameter of horizontal hole is not so expanded. Then, rotor 5 touches casing 1.
Once rotor 5 touches inner surface of casing 1, the surfaces of casing 1 and rotor 5 are grinded by abrasion, and small particles of metal are mixed into powder of process. Actually it is very difficult to detect the happening of this accident. Continuing operation without noticing this accident, huge cost happens to recall contaminated powder and social responsibility to keep safety of food or medicine is impeached severely.
2) The Difficulty of Cleaning
The inserted part of side plate 2 into casing 1, and groove 2b for O ring 11 have space to where powder invades and rots. When sudden lowering of inner pressure in casing 1, rotted powder come out from this space with gas stream, and is mixed with powder of products. According to standard for “Commercial powdered production equipment NSF/ANSI 8”, spaces such as inserted part and groove 2b are to be cleaned regularly by disassembling of the device.
However, casing 1 and side plate 2 are connected with bolts, and tools are necessary to disassemble. And, there is no supporting device for hanging side plate 2, motor mount 8 and geared motor 9. These make difficult to do cleaning work as regular maintenance.
Furthermore, once side plate 2 is disassembled, the position of side plate 2 is changed from the set position initially. Because certain clearance between side plate 2 and casing 1 such as 0.1 mm is necessary for easy disassembling, and this figure of clearance is not negligible small compared with the clearance of 0.2 mm between side plate 2 and casing 1.
Therefore, it is difficult to disassemble side plate 2 for regular cleaning work.